Magnetic comparison circuit



H. J. SCHULTE,l JR

Filed Dec. 25. 1959 /NVENTOA B H. J. .SCHUL TE,JR.

ATTORNEY Timm. WUWSOW KDD n. fnv

MAGNETIC COMPARISON CIRCUIT Jan. 8, 1963 Patented Jan. 8, 1963 3,072,800MAGNETIC COMPARISON CIRCUIT Harry J. Schulte, Jr., Whippany, NJ.,assignor to Bell Teiephone Laboratories, Incorporated, New York, NX., acorporation of New York Filed Dec. 23, 1959, Ser. No. 861,643 11 Claims.(Cl. 307-88) This invention relates to information handling circuitsemploying magnetic memory devices and more particularly to matchingcircuits used for making bit-by-bit comparisons between two trains ofcurrent pulses.

Multiapertured magnetic elements having substantially rectangularhysteresis characteristics have become well known in the art. Such anelement is described, for eX- ample, in the copending application of T.H. Crowley and U. F. Gianola, Serial No. 732,549, led May 2, 1958, nowPatent No. 2,963,591, issued Dec. 6, 1960. By means of suchmultiapertured elements, logic, memory, switching, translationoperations, and the like, are made possible by controlling fluxredistributions within a single unitary magnetic structure. One form ofthe structure com prises a pair of side rails between which a pluralityof transverse members are disposed. The side rails, together with thetransverse members, present a plurality of closed magnetic iiux paths.As a result, tlux induced in one transverse member by an appliedmagnetomotive force may be completed in whole or in part through theside rails and through one or more of the other transverse members. Ithas been found that when all of the available paths are flux limited,that is, when each has the same minimum cross-sectional arca, a fluxinduced in a portion -of the element common to all of the paths will becompleted through a flux path defined by the nearest availablestructural member without regard to the magnitude of the appliedmagnetomotive drive force. Thus, by ap rplying signals to selected onesof a plurality of windings inductively coupled to various transversemembers and side rail portions, these structural members can be made toremain in a given iiux condition while iluX changes occur in otherselected structural members. The flux changes occurring in selectedtransverse members and side rails may then be utilized to induce outputsignals in windings coupled to these structural elements to realizeparticular control functions.

A bit-by-bit comparison of trains of current pulses representing binaryinformation is a frequent and important operation in informationhandling and computation processes generally. Comparison circuits inwhich two input sequences A and B may be compared and particular outputsignals generated as determined by the identity or lack of identitybetween the two sequences are well known. One such circuit employingvacuum tubes provides a half-adder circuit for each bit of each numbersequence. When the outputs of all of the half adders as determined bysuitable AND circuit means are zero, the two numbers being compared areindicated as |being equal. Such a circuit is described, for example, byR. K. Richards, in Arithmetic `Operations in Digital Computers (D. VanNostrand Company, Inc., New York, 1955), at page 291. A circuit such asthere described for performing comparison functions depends, however, onconsiderable power expenditures to operate the various circuits of thevacuum tubes employed, and more importantly, requires that power becontinuously applied if a memory function is also to be realized in thecomparison circuit. The situation is considerably improved `bysubstituting wellknown magnetic cores to perform both the switching andther memory functions. However, in this case also irnprovement may beachieved from the viewpoint of power requirements, ease of fabrication,initial cost, and the like. Thus the elimination of diodes, connectingcircuitry, and other circuit components incident to the use of magneticcores would represent a considerable advance in the comparison circuitart.

Accordingly, it is an object of this invention to provide a new andimproved comparison circuit requiring only a single magnetic elementIfor performing switching functions.

'It is another object of this invention to accomplish the comparison oftwo binary numbers to determine whether the two numbers are identical.

It is yet another-,object of this invention to provide a newv andimproved information handling circuit utilizing both the logic andmemory capabilities of multiapertured magnetic elements.

It is a further object of this invention to provide a new and novelcomparison circuit which realizes a substantial reduction in circuitcomponents.

The foregoing and other objects of this invention are realized in oneillustrative embodiment thereof for per- :forming a comparison and otherfunctions utilizing a single multiapertured structure as the memory andswitching element. The structure is fabricated from a magnetic materialhaving substantially rectangular hysteresis characteristics and presentsa sequence of ux limited ux legs. A normal flux condition is establishedthrough two adjacent legs around a comparison aperture in one directionby a read-out drive. Subsequently, a clock drive is appliedsimultaneously to both the rst and the last legs of the structure. Theflux paths available in the multiapertured structure at this time aresuch that the switching ux so induced from either end of the structureis not able to cause a reversal of the normal ilux around the comparisonaperture. Whether such a reversal occurs and from which end isdetermined by the identity between bits of corresponding bit pairs of Aand B sequences of vinput current pulses introduced into the circuit inphase with the clock pulses. A pulse representative of a bit from eachsequence is applied via a pair of input circuits having windings coupledto the structure to control ux reversals around the comparison apertureby drives from either end of the structure. Thus, if an identity ispresent between a particular bit Ai and a bit Bi of a bit pair, then ailux switching is again prevented around the comparison aperture fromeither end of the structure. On the other hand, if a mismatch betweenparticular bits occurs, the clock drive from one of the ends willreverse the normal flux around the comparison aperture. -From which endthe reversal occurs will depend upon which of the particular bits ispresent. A bit-by-bit comparison continues in this manner until each ofthe corresponding bits of the two sequences has Ibeen compared or untila mismatch has been detected.

After the termination of the bit pairs being compared, the read-outdrive is again applied to the ilux loop presented by the comparisonaperture to reset the flux therearound to its normal condition. If theresetting causes a flux switching around the comparison aperture anoutput voltage signal is generated in an output winding coupled theretoindicative of the mismatch present between at least one pair of bits ofthe A and B sequence of bits. If no flux switching results from theapplication of the read-out pulse, the absence of a signal on the outputwinding is indicative of a match between each bit of the bit pairs beingcompared. After a mismatch has occurred between the bits of any one ofthe bit pairs and thereby caused a reversal from the normal fluxcondition around the comparison aperture, the reversed flux conditioncannot be restored to its previous condition by either a match or amismatch between subsequent bit pairs, the restoration beingaccomplished only by the succeeding read-out operation.

It is thus a feature of this invention that drive windings are coupledto a first and a last leg of a multiapertured magnetic structure and areserially connected in a clock drive circuit. The structure is so formedthat when a clock pulse is applied to the clock circuit a magnetomotivedrive is induced from both ends of the structure, either of whch drivesmay be operative to cause a flux switching around a selected comparisonaperture of the structure. The availability of flux closure pathsnormally prevents such a flux switching around the cornparison aperture.However, when flux closure paths are denied to the switching flux fromeither side of the structure as controlled by a pair of simultaneouslyapplied information input drives, a ux switching is caused around thecomparison aperture.

1t is another feature of this invention that a pair of input circuitsare coupled to a multiapertured magnetic structure in such a manner thatif input signals are present on both or neither of the input circuits,flux switching around a selected comparison aperture of the structure bya simultaneously applied drive from both ends of the structure isprevented. If a signal appears on either one of the circuits whenneither circuit should have a signal thereon, or, conversely, if nosignal appears on either one of the circuits when both of the circuitsshould have signals thereon, at the time of the simultaneously applieddrives, one of the latter drives will cause a ux reversal around thecomparison aperture to generate an output signal in an output windingthreading the comparison aperture.

This invention, together with the foregoing and other objects andfeatures thereof, will be better understood from a consideration of thedetailed description of one illustrative embodiment thereof whichfollows, when taken in conjunction with the accompanying drawing, thesinge FIGURE of which depicts a specific comparison circuit according tothe principles of this invention.

The drawing depicts a multiapertured magnetic element 11 which comprisesside rails 12 and 13 and transverse legs 14 through 19. The side rails12 and 13 are divided by the legs 14 through 19 into control portions12a, 12b, 12d, 12e, 13a, 13b, 13d and 13e and into switching portions12e and 13e. Additionally, legs 14 and 15 and side rail control portions12a and 13a define aperture 21; legs 15 and 16 and side rail controlportions 12b and 13b define aperture 22; legs 16 and 17 and side railswitching portions 12e and 13e define aperture 23; legs 17 and 1S andside rail control portions 12d and 13d define aperture 24; and legs 18and 19 and side rail control portions 12e and 13e define aperture 25.The element 11 is advantageously formed of a magnetic material havingsquare loop hysteresis characteristics and the legs are flux limited,that is, all of the legs have substantially the same minimumcrosssectional areas. A magnetic element of the character contemplatedherein is described in detail, for example, in the copending applicationof T. H. Crowley and U. F. Gianola referred to previously herein.

Input windings 31 and 32 are inductively coupled to side rail controlportion 13a and to leg 18, respectively, while input windings 33 and 34are inductively coupled to leg 15 and to side rail control portion 12e,respectively.

Clock windings 35 and 36 vare inductively coupled to legs 4 and 19,respectively. A read-out winding 37 is inductively coupled to side railswitching portion 12e, and au output `winding 3S is inductively coupledto side rail switching portion 13e. Additionally, the output winding hasoutput terminals 61 connected thereto.

An input pulse source 41 is provided to transmit an A series ofinformation pulses simultaneously to the input windings 31 and 32 via afirst information input circuit S4, which circuit connects the latterwindings in series. An input pulse source 42 is provided to transmit a Bseries of information pulses simultaneously to the input windings 33 and34 via a second information input circuit 55, which circuit connects thelatter windings in series. A clock pulse source 43 is provided totransmit a series of clock pulses to the clock windings 35 and 36 via aclock circuit 56, which clock circuit connects the clock windings 35 and36 in series. The timing of each of the input pulse sources 41 and 42and the clock pulse source 43 is controlled by a timing circuit 45 whichis connected to the sources 41, 43 and 42 by conductors 51, 53 and 52,respectively. A read-out pulse source 44 is connetced via a read-outcircuit 57 to the read-out winding 37. Each of the circuits 54, 55, 56and 57 is connected at its other end to ground. The pulse sources 41through 44 may comprise any suitable circuits well known in the artcapable of providing pulses of the magnitude and polarity to behereinafter described and are consequently represented by block diagramsonly. Similarly, the timing circuit 45 may comprise any well-knowncircuit capable of synchronizing the energization of the pulse sourcesto which it is connected, and it is therefore also represented in blocl;diagram form.

Bearing in mind the foregoing organization of the depicted embodiment ofa comparison circuit according to the principles of this invention, adetailed description of an illustrative operation of the circuit willnow be set forth.

Initially a positive pulse from the read-out pulse source 44 generates,by means of the readout winding 37, a remanent saturation ux through thelegs 16 and 17 in a clockwise direction as viewed in the drawing, aboutthe aperture 23, which aperture 23 may be designated for purposes ofdescription as the comparison aperture. This saturation ux and itsdirection is represented in the drawing by the broken line 23' and itsarrowheads. With the establishment of the normal tiux state about thecomparison aperture 23, the circuit is prepared for the in troductiontherein of the sequences of information bits, the pairs of which are tobe compared.

The first illustrative operation which will be described is one in whicha match occurs between the bits of the pair of bits being introducedinto the circuit, the particular bits each comprising binary 0s. In theconventional manner, the latter values will be represented on the inputcircuits by the absence of signals during the input interval.Accordingly, during this interval no signals will appear on theinformation input circuits 54 and 55 and no drives will be applied tothe magnetic element 11 by the windings 31, 32, 33 or 34. During eachinput interval, however, a positive clock pulse is applied from theclock pulse source 43 to the clock windings 3S and 36 via the clockcircuit 56. The latter windings are in a sense with respect to the legs14 and 19, respectively, that a magnetic flux is induced in the latterlegs in the direction indicated by the arrows 14' and 19', respectively.Flux closure for the latter ux is readily found through the adjacentlegs 15 and 18, respectively, since these legs provide the shortestclosure paths and also in view of the fact that no other magnetic drivesare being applied to the element 11 to interfere with such closure.Accordingly, as a result of the clock drive presently being applied, theremanent flux around the comparison aperture is left undisturbed. Duringthe next succeeding input interval, should the clock pulse from thesource 43 again be the only drive applied to the element 11, that is, ifa match again occurs between a pair of 0 information bits, the remanentilux around the comparison aperture will again be lett undisturbed. Amatch may also occur between the bits of a pair of information bits wheninput signals representative of those bits appear on both of the inputcircuits 54 and 55 during the input interval. ln this case a positivecurrent pulse is supplied from each of the input pulse sources 41 and 42representative of binary 1s. These pulses are timed to occursimultaneously with the clock pulse from the clock pulse source 43 by acontrol pulse supplied from the timing circuit 45. The inp-ut pulseapplied to the winding 3K1 exerts a magnetomotive force on the side railcontrol portion 13a of the side rail 13 in a direction represented bythe arrow 31. However, the winding 31 is provided with the same numberof turns as the clock winding 35 which, as may be determined from thedrawing, is at the same time therefore exerting an equal magnetomotiveforce in the opposite direction on the leg 14. The two applied forcesare thus cancelied out. Since, as was previously described, the circuitand magnetic element 11 are symmetrical, the same cancellation ofmagnetomotive forces exerted by the windings 36 and 34 occurs as aresult of the current pulse being simultaneously applied to the circuit55. The magnetomotive force on the side rail control portion 12e exertedby the pulse on winding 34 is in a direction represented by the arrow34. The winding 34 is also provided with the same number of turns as thewinding 36. The eiectiveness of the clock pulse to cause any fluxchanges in the magnetic element 11 from either end of the structure hasthus been counteracted. The magnetomotive forces generated by the inputpulses in the windings 32 and 33 of the input circuits 54 and 55,respectively, on the other hand, are able to induce a switching flux inthe legs 15 and 18, respectively, in the direction as represented by thearrows 1S' and 18. Since no drives are presently effective to preventit, the switching flux so generated nds ready closure through the endlegs 14 and 19. Although closure paths through the legs 16 and 17 forthe switching ux could also be available, the latter legs are alreadyllux saturated in the direction of the switching ux by the previouslyapplied read-out pulse during the read-out phase. Accordingly, theremanent flux around the comparison aperture 23 is also left undisturbedwhen simultaneous drives are applied as a result of energizing currentpulses applied to the two input circuits 54 and 55 and to the clockcircuit 56.

A mismatch between information bits of the sequence of information pairsbeing compared occurs when either one of the input circuits 54 or 55alone has an input current pulse applied thereto. This is indicative ofthe fact that a binary l occurs where a O should occur in one of thesequences kof bits or, conversely, a 0 occurs where a l should occur.Since the circuit according to this invention as well as the magneticelement 11 is symmetrical, a description of the operation of the circuitwhen a signal appears only on one of the input circuits also provides anunderstanding of the operation of the circuit when an information signalappears only on the other input circuit. When a signal representative ofan information bit l is applied to the input circuit 54 alonesimultaneously with the applied clock pulse to the clock circuit 56 thesame cancellation of magneto- `motive drives generated in the windings31 and 35 occurs as was described previously herein. Thus no effect ofthese drives is had on the magnetic states of the element 11 from theleft side as viewed in the drawing.

However, since at this time no cancelling drive is being applied as aresult of a current in the input winding 34, the clock pulse in theclock Winding 36 is effective to apply a magnetomotive drive to the leg19 and maintain a saturation ux in that leg in the direction representedby the arrow 19'. The latter leg is thus denied.l Aas a closure pathforthe switching ux induced in the leg 18 by the input current in thewinding 32. Due to the ilux limited nature of each of the available uxpaths presented in the element 11-at least some of the switching fluxinduced in the leg 18 iinds a closure path by switching flux in the siderail switching portion 13a of the side rail 31 and the leg 16. Thedirection of part of the iiux around the comparison aperture 23 is thusleft disturbed by a mismatch occunring in the information bit pairsbeing compared.

The pulses transmitted from the pulse sources 41 through 44 are ofsuicient magnitude to magnetically drive the element 11 beyond the kneeof its hysteresis loop in order to achieve the required switchingaction.

It may also be demonstrated that another match or a series of matchesfollowing a single mismatch will be ineffective to restore thesaturation ilux around the comparison aperture to its normal state.Thus, subsequent matches will again merely affect the flux aboutapertures v21 and 25, while subsequent mismatches tending to switch theflux from the end of the element 11 in which the switch occurred duringthe initial mismatch will have no further eitect upon the flux aroundthe comparison aperture. A subsequent mismatch tending to switch the uxfrom the other end of the element 11 will cause a flux switching tooccur in whichever of the legs 16 and 17 is closer to the other end butwill have no eect upon the ilux conditions of the side rail switchingportions 12C and 13C.

During a subsequent read-out phase of operation a read-out pulse isagain applied to the read-out circuit 57. As a result, the magnetomotivedrive developed in the read-out winding 37 restores the remanentsaturation ilux around the comparison aperture 23 to its normal state.This restoration involves a flux switching in the side rail switchingporting 13e of the side rail 13 to which the output winding 38 iscoupled. An output signal is induced in the latter winding 3S as aresult of the restoration of the normal llux around the aperture 23,which output signal is indicative that a mismatch occurred in thesequence of information signals being compared. Manifestly, an outputsignal of the opposite polarity was also developed in the output winding38 when the normal flux in the side rail switching portion 13C was firstdisturbed at the time when the mismatch occurred. The latter signal mayeither be suppressed by the use of suitable unidirectional currentmeans, not shown in the drawing, or may be used instead of or inconjunction with the signal so developed during the read-out phase asdictated by considerations of the system of which the present inventionmay comprise a part.

In the foregoing description of representative operations of acomparison circuit according to this invention a particular order ofoperations was assumed for purposes of description. Thus, it was firstassumed that a match represented by the absence of signalson the inputcircuits occurred, then a match represented by the presence of inputsignals on both of the input circuits was assumed, and nally it wasassumed that an input signal was present on either one of the inputcircuits alone, each simultaneously with the applied clock drive. Inthese operations particular flux switchings and closures were assumed,and the ux behavior described in each case provides a suicient theoreticexplanation, bearing in mind the flux limited nature of each ilux pathof the magnetic element 11. It is to be understood, however, that theactual ilux behavior within the physical structure of the element 11 maybe considerably more complex; however, the details of the magneticphenomena within the element 11 are not necessary for an understandingof the organization of the present invention and the manner of itspractice. Further, it is obvious that the particular llux distributionwithin the element 11 is in part determined by the particular switchinghistory, that is, the particular sequence of the match ormisaovaaoomatch situations. Accordingly, the particular fluxdistribution need not necessarily be identical to those described aboveafter each input interval. However, each distribution pattern may bedescribed in terms of the illustrative operations and sequence describedabove; the flux limited nature of each fiux path of the element 11insuring that fiux switching occurs in the side rail switch-A ingportions 12e and 13e only as the result of and at the times ot" theparticular combinations of input signals described above.

What has been described is considered to be only one illustrativeembodiment of the present invention. Accordingly, it is to be understoodthat various and numerous other arrangements may be devised by oneskilled in the art without departing from the spirit and scope of thisinvention.

What is claimed is:

l. An electrical circuit comprising a magnetic element havingsubstantially rectangular hysteresis characteristics, said elementpresenting a sequence of fiux legs, means for inducing a normal fiuxcondition in a switching portion of said element between a central pairof adjacent ones of said iiux legs, means for inducing a drive fiuxsimultaneously in a first and a last leg of said sequence of flux legs,a first input means for simultaneously counteracting said drive linx insaid first leg and preventing closure of said drive flux in said lastleg eX- cept through said switching portion of said element, a secondinput means for simultaneously counteracting said drive flux in saidlast leg and preventing closure of said drive fiux in said first legexcept through said switching portion of said element, and an outputwinding inductively coupled to said switching portion of said element.

2. An electrical circuit comprising a magnetic element havingsubstantially rectangular hysteresis characteristics, said elementhaving a sequence of flux legs to present a plurality of fiux paths,each of said flux paths being flux limited to the same fiux magnitude,means including a read-out pulse source operable in a first phase ofoperation for inducing a normal ux condition in a switching portion ofsaid element, means including a clock pulse source for inducing a drivefiuX simultaneously in a first and a last leg of said sequence of fluxlegs, a first input means including a first input pulse source forsimultaneously counteracting said drive flux in said rst flux leg andpreventing closure of said drive flux in said last leg except throughsaid switching portion of said element, a second input means including asecond input pulse source for simultaneously counteracting said drivelinx in said last leg and preventing closure of said drive iiux in saidfirst leg except through said switching portion of said element, and anoutput winding nductively coupled to said switching portion of saidelement energized responsive to linx switching in said switching portionof said element when said read-out pulse source is operated in a secondphase of operation for generating an output signal.

3. A comparison circuit comprising a magnetic element havingsubstantially rectangular hysteresis characteristics, said elementpresenting a sequence of flux legs, a read-out winding on a switchingportion of said element between a central pair of adjacent ones of saidfiux legs, means for applying a read-out pulse to said read-out windingfor inducing a normal liux condition in said switching portion, aserially connected first and second drive winding on a first and a lastux leg, respectively, means for applying a clock pulse to said first andsecond drive windings for inducing a drive flux in each of said firstand last linx legs, a first input winding on a control portion of saidelement between said first flux leg and its adjacent leg, a second inputwinding on a control portion of said element between said last linx legand its adjacent leg, a third input winding on the leg adjacent saidfirst leg, a fourth input winding on the leg adjacent said last leg, afirst input circuit means including a first input pulse source and saidiirst and said fourth input windings for controlling fiux switching insaid switching portion of said element, a second input circuit meansincluding av tral adjacent tiux legs, said first flux leg and itsadjacent,

ux leg, and said last fiux leg and its adjacent flux leg.

5. An electrical circuit comprising a magnetic element of a materialhaving substantially rectangular hysteresis characteristics, saidelement comprising a sequence of liux legs including a pair of centraladjacent flux legs connected by switching portions of said element, afirst linx leg connected to an adjacent fiux leg by first controlportions of said element, and a last fiuX leg connected to an adjacentflux leg by second control portions of said element, a read-out circuitincluding a read-out winding on one of said switching portions, a clockcircuit including a clock winding on each of said first and said lastfiux leg, a first input circuit including input windings on one of saidfirst control portions and said leg adjacent said last flux leg,respectively, a second input circuit including input windings on one ofsaid second control portions and said leg adjacent said first flux leg,respectively, and an output winding on the other of said switchingportions.

6. A comparison circuit comprising a multiapertured magnetic elementhaving a pair of side rails with a plurality of flux legs transverselydisposed in a spaced relationship therebetween, said side rails and fluxlegs presenting a plurality of fiux paths, all of said fiux paths beingflux limited to the same fiux magnitude, means for inducing a normalflux condition in a switching portion of one of said side rails betweenan interior pair of adjacent ones of said fiux legs, means for inducinga first and a second drive flux simultaneously in a first and a lastfiux leg, respectively, of said sequence of flux legs, a first inputmeans for simultaneously counteracting said first drive tiux andpreventing closure of said second drive flux except through saidswitching portion, a second input means for counteracting said seconddrive flux and preventing closure of said first drive fiuX exceptthrough said switching portion, and an output winding nductively coupledto said switching portion.

7. A comparison circuit as claimed in claim 6 in which said first inputmeans comprises a first neutralizing winding coupled to a fiux pathincluding said first fiux leg, a first blocking winding coupled to theflux leg adjacent said last fiux leg, and means for simultaneouslyapplying input pulses to said first neutralizing and blocking windings;and said second input means comprises a second neutralizing windingcoupled to a flux path including said last flux leg, a second blockingwinding coupled to the flux leg adjacent said first fiux leg, and meansfor applying input pulses to said second neutralizing and blockingwindings.

8. A comparsion circuit according to claim 6 in which said means forinducing a normal linx condition in said switching portion comprises aread-out winding inductively coupled to a flux loop including saidswitching portion and means including a read-out pulse source forapplying a read-out pulse to said read-out winding.

9. A comparison circuit according to claim 8 in which said means forinducing a first and a second drive flux simultaneously in a first and alast flux leg, respectively, comprises serially connected first andsecond drive windings on said first and last fiux legs, respectively,and means for applying a clock pulse to said first and second drivewindings.

10. A comparison circuit according to claim 9 in which said rst inputmeans comprises a first neutralizing winding nductively coupled to afiux loop including said first flux leg, a first blocking winding on aflux leg adjacent said 9 last iluX leg, and a rst circuit meansincluding a rst input pulse source and said rst neutralizing andblocking windings.

11. A comparison circuit according to claim 10 in which said secondinput means comprises a second neu' tralizing Winding induc'tivelycoupled to a flux loop including said last uX leg, a second blockingWinding on a flux leg adjacent said first flux leg, and a second circuitmeans including a second input pulse source and said second neutralizingand blocking windings.

References Cited in the 111e of this patent UNITED STATES PATENTS Cohenet al. May l5, 1956 Rajchman et al. Aug. 20, 1957 Chen et al. Dec. 31,1957 Lo Dec. 31, 1957 Arsenault et al. Sept. 22, 1959 FOREIGN PATENTSGreat Britain June 3, 1959

1. AN ELECTRICAL CIRCUIT COMPRISING A MAGNETIC ELEMENT HAVINGSUBSTANTIALLY RECTANGULAR HYSTERESIS CHARACTERISTICS, SAID ELEMENTPRESENTING A SEQUENCE OF FLUX LEGS, MEANS FOR INDUCING A NORMAL FLUXCONDITION IN A SWITCHING PORTION OF SAID ELEMENT BETWEEN A CENTRAL PAIROF ADJACENT ONES OF SAID FLUX LEGS, MEANS FOR INDUCING A DRIVE FLUXSIMULTANEOUSLY IN A FIRST AND A LAST LEG OF SAID SEQUENCE OF FLUX LEGS,A FIRST INPUT MEANS FOR SIMULTANEOUSLY COUNTERACTING SAID DRIVE FLUX INSAID FIRST LEG AND PREVENTING CLOSURE OF SAID DRIVE FLUX IN SAID LASTLEG EXCEPT THROUGH SAID SWITCHING PORTION OF SAID ELEMENT, A SECONDINPUT MEANS FOR SIMULTANEOUSLY COUNTERACTING SAID DRIVE FLUX IN SAIDLAST LEG AND PREVENTING CLOSURE OF SAID DRIVE FLUX IN SAID FIRST LEGEXCEPT THROUGH SAID SWITCHING PORTION OF SAID ELEMENT, AND AN OUTPUTWINDING INDUCTIVELY COUPLED TO SAID SWITCHING PORTION OF SAID ELEMENT.